EBV infection induces immortalization of human lymphocytes without killing the cells. On the other hand, treatment of viral genome carrying cells with TPA, or superinfection of such cells with HR-1 virus induces lytic infection which ultimately destroys these cells. Our previous studies indicated that genes residing in the BamHI M fragments (M genes) appear to be playing an important role in the direction of EBV infection, i.e. immortalization or lytic infection. Our recent study also indicated that HRI virus DNA contains 3 BamHI M fragments different in size from standard transforming virus DNA. This suggests that the structural alteration of BamHI M may cause the expression of M genes immediately after superinfection of Raji cells with HRI virus. In this proposal, we plan to study in more detail about the M genes of HR-1 (super-infecting) and B95 (immortalizing) EBV. Detailed structural study of M genes of HR-1 and B95 EBV will be conducted to determine what difference exists between HR-1 M and B95 M genes. To further study transcriptional control of EBV genes including M genes, in vitro transcriptional system will be used. This study may identify any control factors involved in EBV gene transcription. Finally, M gene products will be identified by in vivo labeling of M gene proteins after treatment with and subsequently release from cyclohexamide of superinfected cells or by Cos-1 cell system with pSVOd or pSVO10 vector. The M gene proteins will be expressed in SV40 vector systems or cDNA-bacterial plasmid vector system. The proteins will be purified and tested for biochemical activities such as DNA binding property, protein kinase activity and transcription stimulating activity.